DESCRIPTION: This small grant application seeks to study events leading to th formation of the otic placode using molecular biological techniques. The principal investigator proposes to identify the specific region of the cranial surface ectoderm that is destined to become the otic placode, and to time this event. He further plans to determine whether the presence of hindbrain tissue are necessary or sufficient to induce otic placode formation, and to time the interaction between the tissues. Finally, experiments are proposed to determi if competence to become the otic placode is specific for the placode-forming tissue or more general in surface ectoderm. These experiments are designed in chick embryos, and they require complex surgical manipulations including explanation and implantation of tissues from very young embryos and implantati of sheet barriers. In situ hybridization is the major tool for assessing the presence of the two markers, BMP-7 and Pax-2. The investigator plans to use these gene products as otic-placode-specific markers.